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Detailed study of ELAIS N1 field with the uGMRT - II. Source properties and spectral variation of foreground power spectrum from 300-500 MHz observations
No full textUnderstanding the low-frequency radio sky in depth is necessary to subtract foregrounds in order to detect the redshifted 21 cm signal of neutral hydrogen from the cosmic dawn, the epoch of reionization and the post-reionization era. In this second paper of the series, we present the upgraded Giant Metrewave Radio Telescope (uGMRT) observation of the ELAIS N1 field made at 300-500 MHz. The image covers an area of similar to 1.8 deg(2) and has a central background rms noise of similar to 15 mu Jy beam(-1). We present a radio source catalogue containing 2528 sources (with flux densities > 100 mu Jy) and normalized source counts derived from that. A detailed comparison of detected sources with previous radio observations is shown. We discuss flux-scale accuracy, positional offsets, spectral index distribution and correction factors in source counts. The normalized source counts are in agreement with previous observations of the same field, as well as model source counts from the Square Kilometre Array Design Study simulation. It shows a flattening below similar to 1 mJy that corresponds to a rise in populations of star-forming galaxies and radio-quiet active galactic nuclei. For the first time, we estimate the spectral characteristics of the angular power spectrum or multi-frequency angular power spectrum of diffuse Galactic synchrotron emission over a wide frequency bandwidth of 300-500 MHz from radio interferometric observations. This work demonstrates the improved capabilities of the uGMRT
Spatial and temporal variability in energy and water vapour fluxes observed at seven sites on the Indian subcontinent during 2017
No full textUnder the INCOMPASS project, state of the art eddy-covariance based surface flux measurement systems were installed at eight locations across India. These sites cover different climatic conditions, land use and land cover, and water management practices. Here we present the initial analysis of the measurements taken at seven sites mainly focusing on the year 2017, quantifying for the first time the remarkable contrasts in evaporative fraction across the seasons, climate zones and land management practices of the Indian subcontinent. With the exception of Jaisalmer which is the driest of the places studied, all the sites maintain values of evaporative fraction above 0.5 after the monsoon through to November. By contrast, for those sites with natural vegetation or rain-fed agriculture, evaporative fraction remains below 0.3 for the dry January-May period. In the middle Gangetic Plain area, irrigation and pre-monsoon showers together maintain evaporative fraction above 0.5 between January and June. It is also observed that different variables exhibit different intraseasonal variation characteristics even at one site. Except for Samastipur which is situated in the middle Indo-Gangetic Plains, wind speed shows spectral peak at a smaller time-scale compared to sensible and latent heat fluxes
Fluoride Fiber Sensor With Huge Performance Enhancement via Optimum Radiative Damping at Ag-Al2O3-Graphene Heterojunction on Silicon
No full textSurface plasmon resonance-based fiber optic sensor with multilayer heterojunction is simulated and analyzed. The constituent materials are ZBLAN fluoride core, NaF clad, amorphous Si layer, Ag layer, Al2O3 interlayer, and graphene monolayer. The main idea behind the study is to optimize the radiative damping (i.e., optimum radiative damping, ORD) at the Ag-Al2O3-graphene heterojunction in order to enhance the sensors figure of merit (FOM) as much as possible. The effect of graphene monolayers presence on sensors FOM is also examined. Multiple occurrences of ORD may be achieved by coordinated variation of Ag and Al2O3 layer thicknesses along with light wavelength. Among the several prominent ORD conditions, the combination of 45.3-nm-thick Ag layer, 11-nm-thick Al2O3 layer, and 938.7-nm wavelength leads to a massively large FOM of 31806.65 RIU-1. The above FOM of the FOSPR sensor is nearly six times that for the corresponding prism-based SPR sensor (i.e., 5500 RIU-1) reported earlier with Al2O3 interlayer and MoS2 monolayer at 1200nm. Further, the proposed sensor provides substantially greater FOM compared to existing prism-based and FOSPR sensors
Reconnaissance report on geotechnical effects and structural damage caused by the 3 January 2017 Tripura earthquake, India
No full textAn earthquake of moment magnitude M-w 5.7 shook the northeastern region of India on 3 January 2017 at 14 h:39 min:0.5 s local time. The duration of the tremor lasted for about 5-6 s and had its epicenter in Dhalai District, Tripura, India. Even though the earthquake was of moderate magnitude, it caused damage to several masonry dwellings in Tripura and triggered soil liquefaction, lateral spreading, and landslides near the epicentral area. The sand boils containing appreciable amount of silts were ejected to the ground surface at the Kanchanbari and Kumarghat area due to the liquefaction-induced upward ground water flow. This is possibly the first liquefaction evidence in India induced due to a moderate earthquake magnitude of M-w 5.7. This paper reports the field reconnaissance observations of geotechnical effects and damage to buildings following a shallow, strike-slip earthquake in northeast India on 3 January 2017. In addition, the distribution of surface peak ground acceleration of the earthquake estimated from the empirical equations based on the available data is evaluated and discussed
Offline and Online Scheduling of Jobs with Service and Delay Costs
No full textWe study continuous time job scheduling and server speed scaling problems with focus on minimizing service and job waiting costs. Jobs arrive over time and are to be served by a server. Each job is characterized by its arrival time, service requirement and deadline. The processor incurs service cost, the service cost rate being an increasing convex function of the service rate. Further, the jobs also incur linear waiting cost. We first consider the offline version of the problem where arrival times, requirements and deadlines of all the jobs are known a priori. We propose job scheduling algorithms that minimize the total accrued cost. We then consider the online version of the problem and propose two heuristics. Our problem can be seen as an extension of the well studied speed scaling problem with a delay cost also included
Scheduling Policies for Minimizing Job Migration and Server Running Costs for Cloud Computing Platforms
No full textWe propose job scheduling algorithms to minimize job migration and server running costs in cloud computing platforms offering Infrastructure as a Service. We first consider algorithms that assume knowledge of job-size on arrival of jobs. We characterize the optimal cost subject to system stability. We develop a drift-plus-penalty framework based algorithm that can achieve optimal cost arbitrarily closely. Specifically this algorithm yields a trade-off between delay and costs. We then relax the job-size knowledge assumption and give an algorithm that uses readily offered service to the jobs. We show that this algorithm gives order-wise identical cost as the job size based algorithm. We illustrate the performance of the proposed algorithms and compare these to the existing algorithms via simulation
On the region for the application of passive damping treatment and loss factor enhancement
No full textThe loss factor of a structure is significantly improved by using constrained damping treatment. For a mass efficient design, the damping material is to be applied at suitable locations. The studies reported in literature use the modal strain energy distribution in the viscoelastic material or the strain energy distribution in the base structure as tools to arrive at these suitable locations for the damping treatment. It is shown here that the regions identified through the above criteria need not be suitable for certain bending modes of vibration. A new approach is proposed in which the strain in the viscoelastic material and the angle of flexure are shown to be more reliable in arriving at the locations for the damping treatment. Providing damping layers at identified locations using these parameters results in significant loss factors with minimal added mass
High-resolution intertidal topography from sentinel-2 multi-spectral imagery: Synergy between remote sensing and numerical modeling
No full textThe intertidal zones are well recognized for their dynamic nature and role in near-shore hydrodynamics. The intertidal topography is poorly mapped worldwide due to the high cost of associated field campaigns. Here we present a combination of remote-sensing and hydrodynamic modeling to overcome the lack of in situ measurements. We derive a digital elevation model (DEM) by linking the corresponding water level to a sample of shorelines at various stages of the tide. Our shoreline detection method is fully automatic and capable of processing high-resolution imagery from state-of-the-art satellite missions, e.g., Sentinel-2. We demonstrate the use of a tidal model to infer the corresponding water level in each shoreline pixel at the sampled timestamp. As a test case, this methodology is applied to the vast coastal region of the Bengal delta and an intertidal DEM at 10mresolution covering an area of 1134 km2 is developed from Sentinel-2 imagery. We assessed the quality of the DEM with two independent in situ datasets and conclude that the accuracy of our DEM amounts to about 1.5 m, which is commensurate with the typical error bar of the validation datasets. This DEM can be useful for high-resolution hydrodynamic and wave modeling of the near-shore area. Additionally, being automatic and numerically effective, our methodology is compliant with near-real-time monitoring constraints
Tuning the torque-speed characteristics of the bacterial flagellar motor to enhance swimming speed
No full textIn a classic paper, Purcell Proc. Natl. Acad. Sci. U. S. A. 94, 11307 (1997)10.1073/pnas.94.21.11307 analyzed the dynamics of flagellated bacterial swimmers and derived a geometrical relationship which maximizes the propulsion efficiency. Experimental measurements for wild-type bacterial species E. coli have revealed that they closely satisfy this geometric optimality. However, dependence of the flagellar motor speed on the load and more generally the role of the torque-speed characteristics of the flagellar motor are not considered in Purcell's original analysis. Here we derive a tuned condition representing a match between the flagella geometry and the torque-speed characteristics of the flagellar motor to maximize the bacterial swimming speed for a given load. This condition is independent of the geometric optimality condition derived by Purcell. Interestingly, this condition is not satisfied by wild-type E. coli which swims 2-3 times slower than the maximum possible speed given the amount of available motor torque. Finally, we present experimental data on swimming dynamics of a cargo laden bacterial system which follows our analytical model. Our analysis also reveals the existence of an anomalous propulsion regime where the swim speed increases with increasing load (drag)